Underfloor Insulation

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ROI
3.9-Years
If you have timber floors, mineral wool insulation* can be used between the joists to insulate your floor.  Assuming this is the only insulation measure installed in your house you can reduce the amount of heat loss through your floor by about a half and can therefore reduce your energy bill by about 7 or 8%.

To do this you need to be able to access under the floor via a trap door or you may have to lift all of the floor boards.  Professionally done this is an expensive job and may cost more than £ 1,000 .  DIY it may cost only a £ 100 for materials, but if you have to lift your floor boards, it will be a long and difficult DIY task and will probably end up costing more than £ 100 when you find yourself repairing damage caused by lifting boards.  As a DIY task we have estimated the cost at closer to £ 300 for a smaller house. The first of the tables below indicates the amount of money you could save for various household energy demands and the potential carbon dioxide emission reductions. The second table indicated the payback time if you choose to do this set against various expenditures.
This table shows savings with installing underfloor insulation and the reduction of carbon dioxide emissions for 4 different energy demands, Check your bills to see what you use.
Financial savings by installing underfloor insulation - per year
CO2 emission reduction - kg per year
Below average energy use for heating per year
smaller house or warmer area
Average energy use for heating per year
the average in the UK
Above average energy use for heating per year
larger house or colder area
Source of energy for heating Savings with
original energy use
10000 kWh
Savings with
original energy use
15000 kWh
Savings with
original energy use
20000 kWh
Savings with
original energy use
25000 kWh
⚡ Electricity £0.154 per kWh
£123.2 (293.6kg) £184.8 (440.4kg) £246.4 (587.2kg) £308 (734kg)
⚡ Gas £0.048 per kWh
£38.4 (168kg) £57.6 (252kg) £76.8 (336kg) £96 (420kg)
⚡ Off Peak Electricity £0.075 per kWh
£60 (293.6kg) £90 (440.4kg) £120 (587.2kg) £150 (734kg)
⚡ LPG £0.058 per kWh
£46.4 (184kg) £69.6 (276kg) £92.8 (368kg) £116 (460kg)
⚡ Heating Oil £0.043 per kWh
£34.4 (208kg) £51.6 (312kg) £68.8 (416kg) £86 (520kg)
This table shows the payback time for installing underfloor insulation based on the costs of the fuels used and various cost options for installing the insulation.
Source of energy for heating Insulation install costs
select yours.
Payback time with
original energy use
10000 kWh
(years)
Payback time with
original energy use
15000 kWh
(years)
Payback time with
original energy use
20000 kWh
(years)
⚡ Electric £0.154 per kWh
£0
£500
£1000
£1500
£2000
0
4.1
8.1
12.2
16.2
0
2.7
5.4
8.1
10.8
0
2
4.1
6.1
8.1
⚡ Gas £0.048 per kWh
£0
£500
£1000
£1500
£2000
0
13
26
39.1
52.1
0
8.7
17.4
26
34.7
0
6.5
13
19.5
26
⚡ Economy Electric £0.075 per kWh
£0
£500
£1000
£1500
£2000
0
8.3
16.7
25
33.3
0
5.6
11.1
16.7
22.2
0
4.2
8.3
12.5
16.7
⚡ LPG £0.058 per kWh
£0
£500
£1000
£1500
£2000
0
10.8
21.6
32.3
43.1
0
7.2
14.4
21.6
28.7
0
5.4
10.8
16.2
21.6
⚡ Heating Oil £0.043 per kWh
£0
£500
£1000
£1500
£2000
0
14.5
29.1
43.6
58.1
0
9.7
19.4
29.1
38.8
0
7.3
14.5
21.8
29.1

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0 # Underfloor insulationCompost Hugh 2012-02-26 15:49
Has anyone got a recomendation / advice re spray insulation for suspended floor? I had spray insulation installed on underside of roof very successfully many years ago and zero problems and plenty of pros.
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+1 # underfloorpip gas and oil 2012-03-16 12:03
NO! Don't use spray foam as it will trap condensation and rot the boards. Instead, a foil backed solid insulation with the foil on the warm side is best.
Soft insulation will create some condensation within it so will need a high level of ventilation below it.
I know lots of moving air seems energy inefficient, but rotten joists do not repair themselves!
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0 # insulationLynn Henderson 2011-11-13 17:18
hi i have just had some insulation put in in my bedroom and this site was helpful id like to say the reson why i had insulation put in was not because it was cold, it was because i like taking off my cloths because im always doing u no who... anyway love this site!
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0 # Just had Underfloor insulation put inJennifer Haye 2011-10-18 09:17
Just had underfloor insulation done. I think £1500 might be a bit expensive, I was quoted £10-20 pounds per square meter, but this was dependent on my underfloor depth and access. As my underfloor was about 2 feet I was charged £12 per square meter, it cost me £600 for my 3 bed semi. I went with Andy at draughtyfloors. co.uk, really pleased it's really taken away the chilly feet and draughty feeling I had in the lounge, don't need the fire on now!
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0 # Just had Underfloor insulation put inRichard 2011-10-20 21:36
Thanks Jennifer. That is very useful. I have changed the article accordingly. I think we were quoted on the very high side for this originally. Other prices would be useful if others have them

Cheers richard
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0 # feedbackSuperfoil Insulation 2010-10-05 07:38
I have a site about Underfloor Insulation. So, your information, I think, very much helpful for me. Thank you for nice posting.
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